In the Engine Room on playchess.com our computer chess users test their chess engines with their own opening books and individual system configurations. For kibitzing, e.g. watching games as they are played, there is a limit: you can watch a maximum of 100 games per day.

 

One of the reasons for this is that before there was this limit, many users were automatically watching umpteen thousand games per day and in doing so creating an extremely high demand on the server. Also this should motivate users to try out for themselves their engine configurations by playing them themselves.